The Kindle Fire HD supports Exchange, including the same kinds of security policies as standard Android devices — a new capability in this second Kindle Fire generation. The Email and Calendar apps have simpler UIs than the stock Android versions, to fit better on the small screen. But all the capabilities you need are there, including attachment previews and calendar invites. I was impressed with their quality, given the Kindle Fire HD's decidedly nonbusiness target user. It too can be used in a pinch — if your business is willing to let it in.
Although the Amazon Appstore is curated, the Kindle Fire HD allows sideloading of apps like other Android devices do, so you can install non-app-store apps. A basic version of Quickoffice is available for the Kindle Fire, so you can do basic Office document work with it.
The business connectivity winner. In all cases, assuming you're permitted Exchange access from your media tablet, you have basic email, calendar, and contacts capabilities available. But to do real work routinely, your best option is the iPad Mini.
Security is probably not top of mind when choosing a media tablet, but it should be one of your purchase criteria.
Corporate security. As noted, the iPad Mini has the same strong, enterprise-class capabilities as any iOS device, including a highly compatible VPN client. Also as noted, the Nexus 7 has the moderate security capabilities of most recent Android tablets. The Nexus 7 has Android's standard VPN support, which unfortunately does not include Cisco IPSec VPNs (you'll need to download Cisco's AnyConnect client as well as buy a client access license for it). The Kindle Fire HD provides the basics of Exchange device security, including encryption, and there are even a few VPN vendors' clients for it in the Amazon Appstore — but not for Cisco VPNs.
Note that both the Nexus 7 and Kindle Fire HD, like all Android 3 and 4 devices, come unencrypted. The encryption process requires a full charge, so you can't do it as soon as you open the box, and it takes about 30 to 45 minutes. Note that you can't enable encryption on the Kindle Fire HD in its Settings app; only when you try to connect to an Exchange server that requires encryption are you given the ability to turn on encryption. If you're on the road without a full battery charge the first time you try to connect to Exchange, you'll be out of luck. Like all iOS devices, the iPad Mini is always encrypted, and encryption can't be disabled.
All three media tablets support passwords, so you can prevent unauthorized people from using them.
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